Sandboxie won't open the browser when started

I've used Sandboxie for years, and each version has always installed a desktop shortcut that executed "C:\Program Files\Sandboxie\Start.exe" default_browser when clicked. The result was that my default browser opened, sandboxed, after a five second delay.

But, for the last week or so, clicking that shortcut does nothing. I have uninstalled and reinstalled the current version of Sandboxie and done the same with an older version, but nothing changes.

I'm running a fully up-to-date XP Pro, so of course I'm thinking that a recent update to XP or to my avast free AV or to my default browser Firefox might be the culprit. I haven't done a system restore yet.

Since a right-click on my FF browser shortcut offers the option to "Run sandboxed", I did that but nothing changed. However, clicking "Run sandboxed" on my IE6 shortcut worked fine, opening IE6 in Sandboxed mode just like it always has. (I keep IE6 for an old piece of software that won't run on anything different.)

Has anybody else run into this? Does anybody have an idea about what might be going on?

Check the properties of the shortcut [Right click the icon-properties-shortcut tab]

["<Path>\Start.exe" /box:boxname "<path>\program-name to be sandboxed"] where boxname=sandbox name. The default box is named "default". You can setup multiple sandboxes so that each can sandbox separate program(s).

When the path-name has space in it, you must enclose the entire path+the EXE file in quotes (" "). Example 2 has no space in the latter path-name so quotes are not needed.
Minimum one space before AND after "/box:boxname". No space after the colon, ":".

My summary of those posts is that the "current" version 4.08 of Sandboxie was opening Firefox 27 in an invisible window. Version 4.09.01 Beta was released and resolves incompatibility issues for most people, including me.

I use Firefox 27.01 and Sandboxie 3.72. No problem.
In fact, I'm doing it now writing this reply. I use a shortcut to run sandboxed Firefox too.
Perhaps I use Win7x64 and Sandboxie 64-bit 3.72? And you're 32-bit system?